SCIENCE 8 TOPIC 5

The Six Factors that Set Planets Apart from the Stars

1. Planets have the same westward drift as the stars, but slightly slower than the stars. Venus

2. Planets appear to show retrograde motion (movement in a backward direction).

3. A planet’s distance from the earth changes over time. 4. A planet’s diameter changes over time.

5. A planet’s brightness changes over time.

6. Planets have surface features that change over time.

The Geocentric Model

Why the Geocentric Model was a “bad dog”: 1.Future positions of planets weren’t predictable 2.Terrestrial motions were not accounted for 3.The model became too complicated

The Heliocentric Model Solved all the problems...except for...

“Little problems not explained by the Heliocentric Model: 1.The apparent differences in the sun’s diameter 2.The varying speed of the earth in it’s orbit 3.The moon’s speed and diameter changes

Retrograde Motion of the Planets

How the Coriolis Effect Supported the Heliocentric Model (projectiles)

How the Coriolis Effect Supported the Heliocentric Model (ocean currents)

How the Pendulum’s Movement Supported the Heliocentric Model

How the Pendulum’s Movement Supported the Heliocentric Model Rotating on an axis helped explain the change in terrestrial features

The Ellipse: an orbit that appears as a flattened circle

How Did the Ellipse Solved the Earlier Problems with the Heliocentric model?

The ellipse solved the problems with the apparent differences in the sun’s diameter, the varying speed of the earth, and with the moon’s apparent speed and diameter changes.

The Law of Equal Areas states that equal areas of space are swept by a planet during equal amounts of time.

Why the Moon (or any satellite) Stays in Orbit Around the Earth